Type: button bits, chisel bits, cross bits Model Number: X,XX,EX,EXX,EC,ECC,ESF,ESSF, ... is stable.We can offer a large range of drill bits to suite the changing geology encountered durig project, the details ... ±0.03mm, and of inner surface roughness Ra0.4-0.6. The types of steel tubes include 10#, 20#, 35#, 45 ... overseas customers for Win-Win businesses. DingRun High Quality Drill Bits